The present invention relates to a hydraulic damper or shock absorber adapted for use in a suspension system such as the suspension systems used for automotive vehicles. More particularly, the present invention relates to a hydraulic damper or shock absorber having a continuously variable damping characteristic which is adjustable by a solenoid actuated continuously variable servo valve to vary the damping characteristics between a relatively low level of damping for a soft ride for comfort and a relatively high level of damping for a firm ride for handling.
A conventional prior art hydraulic damper or shock absorber comprises a cylinder which is adapted at one end for attachment to the sprung or unsprung mass of a vehicle. A piston is slidably disposed within the cylinder with the piston separating the interior of the cylinder into two fluid chambers. A piston rod is connected to the piston and extends out of one end of the cylinder where it is adapted for attachment to the other of the sprung or unsprung mass of the vehicle.
Various types of adjustment mechanisms have been developed to generate variable damping forces in relation to the speed and/or the amplitude of the displacement of the sprung mass in relation to the unsprung mass. These adjustment mechanisms have mainly been developed to provide a relatively small or low damping characteristic during the normal steady state running of the vehicle and a relatively large or high damping characteristic during vehicle maneuvers requiring extended suspension movements. The normal steady state running of the vehicle is accompanied by small or fine vibrations of the unsprung mass of the vehicle and thus the need for a soft ride or low damping characteristic of the suspension system to isolate the sprung mass from these small vibrations. During a turning or braking maneuver, as an example, the sprung mass of the vehicle will attempt to undergo a relatively slow and/or large movement or vibration which then requires a firm ride or high damping characteristic of the suspension system to support the sprung mass and provide stable handling characteristics to the vehicle. These adjustable mechanisms for the damping rates of a shock absorber offer the advantage of a smooth steady state ride by isolating the high frequency/small amplitude excitations from the unsprung mass while still providing the necessary damping or firm ride for the suspension system during vehicle maneuvers causing low frequency/large excitations of the sprung mass.
The continued development of shock absorbers includes the development of adjustment systems which provide the vehicle designer with a continuously variable system which can be specifically tailored to a vehicle to provide a specified amount of damping in relation to various monitored conditions of the vehicle and its suspension system.
The present invention provides the art with a continuously variable adjustable hydraulic damper or shock absorber that includes the capability of adjusting the damping rate of the shock absorber between a firm rebound damping force with a soft compression damping force, a soft rebound force with a soft compression damping force and a soft rebound damping force with a firm compression damping force. A solenoid actuated continuously variable servo valve adjusts the damping force characteristics of the shock absorber and has the capability of positioning the damping force characteristics of the shock absorber anywhere between these configurations to provide the continuously variable damping for the shock absorber.
Other advantages and objects of the present invention will become apparent to those skilled in the art from the subsequent detailed description, appended claims and drawings.